This project involves the conduct of therapeutic clinical trials for the treatment of inherited immune deficiencies using hematopoietic stem cell transplantation. We previously reported the successful use of non-ablative conditioning to achieve successful long term engraftment and cure of CGD patients using HLA-matched sibling donors as the source of the hematopoietic stem cell graft. One of the problems with this approach was the high rate (30%) of graft failure or very low engraftment. In 2004 we performed a follow up transplant on an X-CGD child previously transplanted by us who had achieved high level donor T cell engraftment but less than 1% long term myeloid engraftment. We demonstrated successful permanent conversion to almost 100% donor chimerism in the lymphoid and myeloid lineages using conditioning with only busulfan at 10 mg/kg. This strongly supports the use of this approach to rescue low engraftment rather than using a fully myelo- and lympho-ablative conditioning regimen for such salvage therapy. We have now opened a clinical trial to treat patients with immunodeficiencies using either a matched related, matched unrelated, or cord blood product and a tolerance inducing conditioning regimen consisting of Campath 1-H and busulfan with sirolimus for graft versus host disease prophylaxis. For patients receiving an unrelated product, total body irradiation is also added to the regimen. To date we have enrolled five patients. The first patient, a 32 year old male with X linked CGD and underlying renal dysfunction, received a 10 out of 10 HLA matched bone marrow product from an unrelated donor. The patient had slow engraftment with a prolonged period of neutropenia and thrombocytopenia. In addition he developed renal failure after receiving one dose of ambisome for a presumed fungal infection. Although the patient received a second stem cell product from the same donor, and achieved full engraftment by chimerism analysis, the patient subsequently declined further treatment, specifically dialysis, and subsequently expired due to uremia and hyperkalemia at 95 days post transplant. The second patient was a 15 year old male with X-SCID and underlying MAI infection who has failed 4 previous attempts at unconditioned haplotransplantation. For his conditioning, he received ATG instead of the Campath as he had only a cord blood product available to him and given his underlying T cell deficiency along with a slower T cell recovery associated with cord blood products, it was opted to use a T cell depleting agent with a shorter half life. He otherwise received both the radiation and busulfan and has sirolimus for a little over 6 months. The patient is currently two years post transplant and is doing well. He has normal T cell function and is IVIG independent, and is off all immunosuppressives with no evidence of graft versus host disease during any time of the transplant. The third patient to undergo transplant was a 32 year old female with Leukocyte adhesion deficiency. She was conditioned with Campath, Radiation and busulfan along with the sirolimus using a 9/10 unrelated donor product. At the time of transplant, the patient had ongoing infections with multiple resistant organisms including acinetobacter and open wounds involving her inner thigh and abdomen. The patient had previously undergone transplant using her mother as a haplotype donor, but rejected the graft. Although she showed evidence of initial engraftment, it was decided to infuse a stem cell boost after treating the patient with rituximab due to her high titres of HLA antibodies. She achieved one hundred percent engraftment, but died of multiorgan failure after developing a sepsis like picture. No organisms were cultured at the time of death and no evidence of GVHD was seen at autopsy. The exact cause of death has therefore not been determined. A fourth patient with interferon gamma deficiency was enrolled;however during workup was not deemed to be eligible. The fifth patient to be enrolled has P47 deficient CGD and previously failed a transplant using her HLA matched sister, but her sister was no longer eligible to donate. She received radiation, busulfan, and campath and was infused with cells from a 10/10 unrelated donor. She is now one year post transplant with full myeloid engraftment and lymphoid engraftment of 83%. She is doing well now off all immunosuppression, and has had no evidence of GVHD during the transplant period. We are continuing to enroll patients and are anticipating at least one more transplant to be done by the end of this year. Meanwhile, we have been investigating the use of an adenosine A2a receptor agonist. Prior studies have shown that agonists specific to this receptor improve outcomes in ischemia models of tissue damage. In collaboration with the investigators at the University of Virginia who have supplied a specific agonist known as ATLe146, we have been testing this drug in a murine model of graft versus host disease. We have seen benefit in attenuating the onset and severity of GVHD in our F1-parental transplant model and experiments are undergoing to further elucidate the exact mechanism of its benefit. A manuscript has been prepared and submitted for publication. Further studies have shown a role for T regulatory cells as part of the mechanism of the drugs effects. In addition we have found that rapamycin also works to reduce TH17 cells in our model and this data has been submitted for presentation at the annual American Society of Hematology meeting this year. In order to establish a clinical trial using an adenosine agonist, we have explored the use of other similar agonists, in particular, an FDA approved formulation known as Regadenosan, however the effects appear to be very specific to the A2A receptor and apparently metabolites of various formulations can interfere with the agonists role in GVHD and tolerance induction. We are therefore in the process of studying similar but more potent formulations in collaboration with PGX health (previously Adenosine Therapeutics) to test these compounds both as single agents and/or in combination with rapamycin for the prevention and/or treatment of graft versus host disease.